Circuit interrupter



Jan. 25, 1944. H` 5:,- GANO V 2,340,050

CIRCUIT INTERRUPTER Filed NOV. 15, 1940 as 67 @s fos 22 /04 4f. fg `/7 E/f www l BY ATTORNEY I Patented Jan. 25, 1944 OFFICE CIRCUIT INTERRUPTER Harlan S. Gano, Wilkinsburg, Pa., asslgnor to Westinghouse Electric & Manufacturing Company, East Pittsburgh, Pa., a corporation .of

Pennsylvania Application November 13, 1940, Serial No. 365,491

i 11 claims. (cl. 20c-nc) The invention relates, Ain general, to electrical switches or circuit breakers of the type having" an electro-responsive or a thermal trip element for automatically causing the opening of the contacts of the switch or circuit breaker in response to predetermined-overload conditions. In particular, the invention concerns circuitbreakers of the above type which have a trip element compensated for changes in ambient temperature.

In the application for Letters Patent led September 8, 1938, by Oliver S. Jennings and Harlan S. Gano, Serial No. 228,942,"now Patent'No. 2,284,825, granted June 2, 1942, there is described a novel method of mounting the thermal trip element of a circuit breaker and in compensating the same for changes in the ambient temperature of the medium surrounding the circuit breaker. The circuit breaker there described was designed specifically for oil-immersed applications; however, the novel method illustrated there for mounting and compensating the bimetallic trip element is suitable for circuit breakers operating in air also.

The present application concerns an important improvement in the means for mechanically connecting the free end of the compensating bimetal with the main bimetal which actually trips the breaker open. It is desirable to avoid any unnecessary lost motion, friction, or play in the connecting means between the two bimetals, and the present application is concerned specically with a novel connection between these two bimetals. It has been found experimentally that any unnecessary free play, friction, or lost motion in the connecting means intermediate the two bimetals will result in varying characteristics of the main bimetal and successive tripping of the breaker on widely different overload currents. The present invention eliminates all unnecessary Y free play, friction, or lost motion in the connecf` Another object of the invention is the profree play in the connection between the two bimetals.

Another object of the invention is the provision of a circuit breaker with a compensating vision of a connection between the tripping bi- Y metal of a circuit breaker and its ambient temperature compensating bimetal which will eliminate all unnecessary lost motion, friction, and

bimetal located outside the circuit breaker casing so as to be unaffected by the heat generated within the casing of the circuit breaker and a connection between the compensating bimetal and the tripping bimetal located within the casing to eliminate any lost motion, friction, or play between the two.

Another vobject of the invention is the pro` vision of an oil-immersed circuit breaker with a compensating bimetal disposed away from the oi1 immediately surrounding the current carrying parts of the breaker and yet mechanically connected to the tripping bimetal within the region of circulation of such oil -so that there will be no unnecessary lost motion, friction, or free play between the two bimetals.

Another object of the invention is the provision of a circuit breaker with a tripping bimetal which carries the full series current of its respective pole, said tripping bimetal being connected by insulated mechanical means to a compensating bimetal located outside the circuit breaker case in such manner that there is no unnecessary free play, friction, or lost 'motion in the connecting means. i

Another object of the invention is the provision of an insulated mechanical connection between the tripping bimetal of a circuit breaker and its ambient temperature compensating bimetal which will eliminate all unnecessary lost motion, friction, and free play between the two, yet will still allow easy adjustment of one relative to the other.

The novel features that are considered char- I acteristic of the invention are set forth in particular in the appended claims. The inventiony itself, however, both as to structure and operation, together with additional objects and advantages thereof, will be ybest understood from I two bimetals, the bimetals being shown flexed Figure 3 is an enlarged fragmentary sectional view of a modified form of connecting means between the two bimetals as applied to a multipole circuit breaker, the ambient temperature being normal; and,

Figure 4 is a plan view of the trip device shown in Figure 2, the ambient temperature being normal.

Referring to the drawing, particularly to Figure 1 thereof, the circuit breaker comprises, in general, 'a base I, a. cover 3, contact means indicated generally at 5, an operating mechanism indicated generally at 1, and a trip device indicated generally at 9.

The base I is constructed of molded insulating material and forms a support for the various elements of the circuit breaker. The cover 3, which is also constructed of molded insulating material, is secured to the base I by suitable means such as bolts (not shown) which pass through aligned openings formed in the base and cover. End terminals II and I3 are mounted in suitable openings provided in the ends of the base I, Vand these end terminals II and I3 form the means for connecting the breaker in an electrical circuit.

The contact means indicated generally at 5 comprises a stationary contact I5 connected to a conductor strip I1 by means of a screw I9, which also secures the stationary contact I5 to the base I. The conductor strip I1 is electrically connected to the end terminal II by means of a screw 2|. The contact means indicated generally at 5 also comprises a movable contact 23 carried by a resilient switch arm 25, and an arcextinguishing means indicated generally at 21. The arc-extinguishing means 21 is not an important part of the invention, and any suitable type may be used. 1

The movable contact 23 is secured to thefree end of the resilient switch arm 25 by means of a rivet 29, and the opposite end of the switch arm 25 is secured to a channel-shaped movable contact supporting frame 3l by means of a pair of rivets 33. The channel-shaped movable contact supporting frame 3! is pivotally supported by means of a pivot pin 35 to the side walls of a.

metallic U-Shaped main frame 31 secured to the base I by means vof rivets 39 and a plate 4I.

The operating mechanism indicated generally at 'I comprises, in general, 'a bifurcated operating member 43, a releasable cradle 45, a pair of toggle links 41 and 49, a pair of over-center springs 5l, and an operating handle 53.

The bifui'cated operating member 43 has the lower ends of its legs pivotally supported on the side walls of the main frame 31 by means of pivot studs 55. The upper end of the bifurcated operating member 43 has secured thereto an arcuate closure member 51 of molded insulating material, which acts to close an opening 59 provided in the cover 3 ior any position of the bifurcated operating member 43. The handle 53 is formed integrally with the closure member 51 and projects through the opening 59 in the cover 3. A resetting member 6I projects from and is formed integrally with the bifurcated operating member 43, and this member serves to reset the releasable cradle 45 following a tripping operation, as will be described hereinafter.

The releasable cradle 45 is pivotally supported by means of a pivot pin 63 which extends between the side walls of the main frame 31. The releasable cradle 45 has a rearwardly extending portion 65 provided with a, latch nose 61 which is insulated from the releasable cradle 45 by a plurality of insulating plates 69. The releasable cradle 45 is adapted to be normally held in a latched position by means of the trip device l.

The toggle links 41 and 49 pivotally connect the channel-shaped movable contact supporting frame 3| to the releasable cradle 45 in the manner shown in Figure 1 of the drawing, the lower end of the link 49 being pivotally mounted on the movable contact supporting frame 3I by means of the pivot pin 1I, and the upper end of the link 41 being pivotally connected to the releasable cradle 45 by the pivot pin 13. The overcenter springs 5I are connected between lugs 15 formed integrally with the bight portion of the operating member 43, and a knee pivot pin 11 which pivotally connects the toggle links tog'ether.

The operation of the circuit breaker as thus far described is, briefly, as follows. With the parts in the position shown in Fig. l, that is, with the contact means in closed-circuit position and the releasable cradle 45 held in its normally latched position by the tripdevice 9, let it be assumed that it is desired to manually open the circuit controlled by the breaker. The operating handle 53 is moved from the closed position shown in Fig. 1 in a counter-clockwise direction to an open-circuit position at the opposite end of the opening 59. This movement of the oper'- ating handle 53 to open position moves also the operating member 43 in a counter-clockwise direction about its pivot axis 55. As soon as the line of action of the over-center springs 5i crosses the pivot pin 13, which connects the upper toggle link 41 to the releasable cradle 45, the force exerted by the springs 5I causes collapse of the toggle links 41 and 49. The collapse of the toggle links 41 and 49 causes movement of the switch arm 25 in a countersclockwise direction to opencircuit position with a snap action.

In manually closing the circuit breaker, substantially the reverse action takes place. The operating handle, 53 is returned to the closed position shown in Figure l. At a certain point in the closing movement of the operating handle 53 the line of action of the over--center springs 5I crosses the pivot pin 13, and the force of the over-center springs 5I causes the toggle links 41 and 49 to assume their extended or in-toggle position as shown in Fig. 1. Movement of the toggle links 41 and 49 to their extended position causes clockwise movement of the movable contact supporting frame 3| and switch arm 25 to a closed-circuit position with a snap action to effect engagement of the movable contact 23 with the stationary contact I5,

The releasable cradle 45 is always biased in a clockwise direction about its pvot axis 63 by a component of force exerted by the over-center springs 5I, but the trip device 9 under normal conditions holds the releasable cradle 45 in its normally latched position, shown in Fig. 1, against the biasing action of the over-center springs 5I If an overload of predetermined magnitude and duration occurs in the circuit controlled by the breaker, the trip device 9 operates to eiect release of the releasable cradle 45. The member 45, when released, is rotated in a clockwise direction about its pivot axis 63 by the springs 5I, and at a predetermined point in its movement causes the line of action of the overcenter springs 5I to cross the pivot 'pin 13 to efcounter-clockwise movement of the switch arm 25 to open-circuit position with a snap action to interrupt the circuit controlled by the breaker. After an overload tripping operation, the breaker cannot be reclosed without first moving the operating handle 53 to the full open-circuit position. The resetting movement of the operating handle 53 to the full open-circuit position causes the resetting memberl 6I to engage and move :.lie releasable cradle 45 in a. counter-clockwise direction to the position shown in Figure 1, in which it is relatched by the trip device 9.

The trip device 9 comprises a thermally responsive trip element in the form of a. bimetallic strip 19, which is pivotally mounted at its lower end on the base I. The lower end of the bimetallic element 19 is bent at a-right angle and secured yin any suitable manner to a. U-shaped bracket 8|. 'I'he bracket 8| is pivotally mounted -on a U-shaped supporting bracket 83 by means of a pivot pin 85 which extends through the side legs of the brackets 8| and 83. The supporting bracket 83 is seated on the base I and is rigidly secured thereto by a pair of downwardly extending projections 81 (only one being shown) which pass through openings in .the base I and have their lower ends clinched over against a plate 89 engaging the underside of the base I.

The upper end of the bimetal trip element 19 is provided with an adjustable latch element 9| in the form of an adjusting screw, which is threaded through the free'end of the trip element 19. The latch element 9| is normally adapted to overlap the latch nose 01 carried by the releasable cradle 45 to hold the reelasable cradle in its normally latched position shown in Fig. 1. The bi-metallic trip element 19 is connected in series with the contacts I5 and 23 ofthe circuit breaker by means of a pair of flexible series conductors 93 'and 95, so as to be responsive to the current flowing in the controlled circuit. The flexible series conductor 93 has one end connected to the terminal i3, and its other end. connected to the upper free end of the bimetallic trip element 19. The flexible series conductor 95 is secured to the bent foot of the bimetallic trip element 19 at one end, and the other end is secured to a terminalstrip 91. The terminal strip 91 is secured to a horizontal extension or" the mounting bracket 83 by means of a screw 99 (Figure 4). The other end of the terminal strip 91 is connected by flexible series conductors |0I to the resilient switch arm 25.

The circuit through the breaker extends from the left-hand terminal i3 through the exible conductor 93, bimetallic trip element 19, flexible conductors 95, terminal strip 91, eirible conductors I0 I, resilient switch arm 25, through the contacts 23 and l, conductor strip il to the opposite terminal II.

The bimetallic trip element 19 is normally held against rotation about its pivot axis it in the position shown in Fig. l, by means which will be hereinafter described. When an overload of predetermined magnitude and duration occurs in the circuit controlled by the breaker, the binrietallic` trip element 19 is heated by the overload current and flexes in a direction away from the operating mechanism 1 to cause the latch element 9| to release the releasable cradle 45. The releaseof the cradle 45 effects -opening of the circuit breaker in the manner previously described. After the circuit has been interrupted, the bimetallic trip element 19 cools and returns to its normal position shown in Fig. 1,\t0 permit resetting of the circuit breaker as previously described.

The circuit breaker is calibrated at the factory by means of the adjustable latch element 9| so that it will trip open in response to overload currents of definite predetermined magnitude and duration. After the breaker has been calibrated, the adjusting screw 9| is sealed by a suitable sealing material to maintain the calibration permanent.

'I'he bimetallic trip element 19 is, affected by changes in ambient temperature. If the ambient temperature rises, the bimetallic trip element 10 deilects in a direction away fromthe operating mechanism 1 an amount proportional to the rise in ambient temperature. This decreases the amount of latch overlap between the latch element 9| and the latch nose 61, with the result that the breaker will be tripped open either at a. lower current than that for which it was calibrated, or at a given overload current in a shorter period of time. Conversely, if the ambient temperature decreases, the bimetallic trip element 19 will deflect in a direction toward the mechanism 1 and will tend to increase the amount of latch overlap between the elements 9| and 91, with the result that the vbreaker will be tripped open either at a higher current than that for which it waspcalibrated, or at a given overload current after a longer period of time.

In order 'to prevent changes in ambient temperature from affecting the trip characteristic of the trip element 19, and to insure that the `break- Ver will 4be trippedI open in response to definite ,predetermined overload conditions, irrespective of changes in ambient temperature, there is provided an ambient temperature compensating means comprising a bimetallic strip |03, and a mechanical connecting means indicated generally at |05 interposed between the bimetallic strip opening in an offset horizontal projection ||3 ofr the U-shaped bracket 8|. The insulator ||I is rigidly secured to the horizontal projection H3 by means of a lockwasher ||5 and a nut ||1. A. spring ||9 which is coiled around the pivot pin 85 'biases the U-shaped bracket 8| in a clockwisel direction around the pivot pin 85 so that the point of contact between the Vadjusting screw |09 and the insulator |I| is always under compression.

An opening IZI in the base is provided to permit engagement between the elements comprising the mechanical connecting means |05, but this opening |2| is made as small as possible to minimize any heat transfer from the interior of the circuit Ibreaker casing to the bimetallic strip |03. The insulation effect of the insulator further helps to minimize heat transfer between the elements in the interior of the circuit breaker casing and the bimetallic strip |03.

An important feature of the invention is the location of elements III and |09 so that their point of contact is as close as possible on'a center line connecting the pivot pin 85 with the fixed part of the bimetallic stripl |03 nearest the free ments comprising the mechanical means Ill is greatly reduced, thus reducing friction and resulting in more uniform breaker performance.

The operation of the ambient temperature compensating means is briefly as follows. If the ambient temperature rises, the bimetallic trip element 19 ilexes toward the left away from the operating mechanism 1. However, the bimetallic strip |03 is arranged so that it flexes downwardly away from the base I, thus permitting the coil spring ||9 to rotate the U-shaped bracket 0| clockwise around its pivoting axis 05 and hence to compensate for the ambient temperature deflection of the bmetallic trip element 19. Fig. 2 illustrates the position of the elements when the ambient temperature is high. Similarly, if the ambient temperature decreases, the bimetallic trip element 19 deilects toward the operating mechanism 1, but at thepsame time the bimetallic strip |03 defiects upwardly toward the base I and rotates the U-shaped bracket 8|, and element 19 which it supports, about its pivoting axis 85 in a counter-clockwise direction against the biasing action of spring IIS, to compensate for the decrease of ambient temperature. It will thusbe seen that the bimetallic strip |03 always maintains the same amount of latch overlap between the latch element 9| and the latch nose 61 irrespective of any change in ambient temperature, so that the breaker will always be tripped open in response to definite predetermined overloads, in-

dependently of any change in ambient temperature.

The circuit breaker described above was specically designed for oil-immersed applications, but the invention -is not limited to such applications and may be applied to circuit breakersoperating in other mediums or in air. In oilimmersed applications, however, it is essential that the compensating bimetal |03 be placed in a region away from the vicinity of the warm current-carrying' parts of the breaker, and be maintained at the ambient temperature of the oil surrounding the breaker. The particular mounting arrangement of the bimetallic strip |03 fulfills this condition, and also prevents hot oil in the vicinity of the current-carrying parts of the breaker from coming in contact with the compensating bimetallic strip |03. The bimetallic strip |03 is, therefore, constantly maintained at the ambient temperature of the oil surrounding the circuit breaker casing and is not greatly affected by the heat of the hot oil in the interior of the casing or by the circulation of such hot oil. The opening |2| in the base is made as small as possible, and the insulator ||I helps to insulate any heat transfer. The physical size of the insulator and the adjusting screw |09 also helps to prevent any circulation of oil through the opening |2| in the base Consequently, heat generated Within the circuit breaker casing does not aiect the bimetallic strip |03, and there is practically no circulation of hot oil through the opening |2|.

The adjusting screw |09 is adjustable from outside of the circuit breaker casing and serves to adjust the trip characteristic of the bimetallic trip element 19. Turning the screw in towards the base I', serves to decrease the amount of latch overlap between the latch element 9| and the latch nose 61, and to result in the breaker tripping open more quickly than before for the same current, and also tripping open at a lower steadily maintained overload current. Turning the screw |09 out away from the base I, serves asiento to increase the amount of latch overlap between the latch element 0| and the latch nose 01, and to result in the breaker tripping open more slowly than beforefor the same current, and also tripping open at a higher steadily maintained overlord current than before.

By varying the deflection characteristics oi the bimetallic strips |03 and 19 with respect to each other, the bimetallic trip element 19 may be under, fully, or overcompensated for changes in the ambient temperature, or arranged to give any other desired characteristic of compensation.

Fig. 3 is a modification of the invention as applied to a multi-pole breaker similar in mechanism to the breaker described in connection with Fig. 1, but having a common trip bar which may be actuated by the individual trip mechanism of any pole. Each pole of the multi-pole breaker has its individual tripping mechanism, which upon an overload occurring in that pole will slightly rotate the common trip bar to trip the breaker open. The view is cut away to show only one pole with its associated trip mechanism, since the multi-pole structure may be as shown in my Patent No. 2,162,577, issued June 13, 1939.

In the form of the invention illustrated in Fig. 3 there is a cylindrically shaped common trip bar |23, made of molded insulating material, which is pivotally mounted and rotatable about its longitudinal axis. This common trip bar |23 extends across all the poles of the breaker and may be actuated by the tripping mechanism associated with any pole to trip the breaker open upon an overload occurring in that pole of the breaker. Thecommon trip bar |23 has a number of horn-shaped upwardly extending projections |25 formed integrally with the trip bar, one for each pole, each of which engages an adjustable screw |21 threaded through the free end of the bimetallic trip element |29 for that pole. The bimetallic trip element |29, as before, carries the full current of its respective pole, the flexible conductor 93 serving to carry the full current of the pole to the free end of the bimetallic trip element |29, whence the current passes through the bimetallic trip element |29 to be nally carried 0H by the iiexible conductors 35 to the terminal strip 91, and thence to the switch arm 25 by means of the flexible conductors |0|.

When an overload occurs in the pole, the overload current, passing as it doesthrough the loimetallic trip element |29, serves to heat the same and to flex the bimetallic trip element |29 to the right. This ilexing causes the adjustable screw |21, engaging the horn-shaped projection |25 for its pole, to partially rotate the common trip bar |23 in a. clockwise direction about its longitudinal axis. The partial clockwise rotation of the common trip bar |23 also rotates in a clockwise direction a iin-shaped metallic insert |3| rigidly embedded in the trip bar |23 adjacent the center of the bar. The left-hand end portion of the arcuate edge of the fin-shaped metallic insert |3| normally supports the end |33 of the horizontal extension |35 of a pivotally mounted U-shaped bracket or latch |31, as shown in Fig. 3. The horizontal extension |35 of the pivotally mounted U-shaped bracket |31 has a slot |39 therein, which is slightly wider than the iin-shaped metallic insert |3I and disposed directly over the insert I3I. A pivot pin III, supported between the two side walls of a U-shaped main frame |43 ot the breaker (the irame |43 being similar to the main frame t1 described in connection with Fig. 1), serves to pivotally mount the U-shaped bracket 51. Coiled about the pivot pin @4| is a spring i433, one end of which biases the fin-shaped metallic Ainsert |3| and the common trip bar 23 in a counter-clockwise direction about thelongitudinal axis of the common trip bar 23. The other end of the spring M3 engages a rearwardly entending portion i531 oi the Unshaped bracket i231, and, as a result, this end of the spring lilo .biases the U-shaped bracket it?! in a counter ready described in connection with Fig. l, and

is always biased in a clockwise direction about its pivot axis (not shown). The upper end ci the slot i normally engages and latches a latch nose i153 or" the releer-sable cradle ibi to permit the breaker to be normally operated.

When an overload current passes through any pole ci the multi-pole breaker, the overload current passing through the bimetallic trip element' i129 :tienes the same to the right. This dering oi the bimetallic trip element to the right serves to partially rotate the common trip bar l in a clockwise direction about its longitudinal anis. This partial rotation ci the trip bar also rotates the iin-shaped metallic insert lili, and permits the horizontal extension i3d oi the U-shaped bracket itl (the iJ-shaped-bracket tbl being biased in a counter-clockwise direction about the pivot pin lili bythe spring itil), to drop down, the n-shaped metallic insert lill then projecting up through the slot The counter-clockwise' rotation of the U-shaped bracket l 31 serves to disengage the latch nose i of the releasable cradle lill from the upper end of the slot will, and to permit the releasable cradle l5| to fly upward and to trip the breaker open in a manner identical to that described in connection wtih Fig. 1.

When it is desired to reset the breaker, the operating handle (not shown) of the breaker is moved to the full open position, and in a inanner identical to that already described in connection with Fig. 1,- the releasable cradle ibi is moved in a counter-clockwise direction about its pivot axis (not shown). Near the end oi its counter-clockwise travel the lower end of the nose |53 engages the lower end of the slot |639 and forces the U-Shaped bracket 31 in a, clock- Wise direction about its pivot axis IM against the biasing 4).ction of the spring |45. This clockwise rotation of the U-shaped bracket |31 raises the horizontal portion |35; and the spring H15,

biasing the iin-shaped metallic insert |3| in a counter-clockwise direction about the longitudinal axis of the common trip bar |23, forces the iin-shaped, metallic insert |3| under the end |33 of the horizontal portion |35 of the latch |31. The clockwise rotation of the U-shaped bracket or latch |31 brings the upper edge of the slot |49 over the line of action of the latch to latch the'releasable cradle itl until the next overload omration occurs.

The adjustable screw l21 permits the circuit breaker to be calibrated at the factory so that the breaker will trip open in response to overload currents of definite predetermined magnitude ,and duration. After the breaker has been cali brated, the adjusting screw |21 is sealed by a suitable sealing material to maintain the calial nose |53 of the releasable cradle |5|, so that when the operating handle (not shown) is released or is moved to the closed-circuit position the releasable cradle will again have its nose |53 engaged by the upper end of the slot |49 bration permanent.

The mechanical connection between the bime= tallic trip element [|29 and the ambient temu perature compensating bimetallic strip .lill com prises a metallic adjusting screw ibis' threaded through the free end of the bimetallic strip tilt, through the center of which is rigidly soldered or otherwise suitably fastened a piece oi steel piano vwire itil, which passes loosely through an insulating bushing' tot and is soldered or other wise suitably secured at its other end to a washer iti. The insulating bushing tot passes through an opening provided in the odset horizontal portion liti of the il-shaped bracket iii. il nut is threaded on to thelower end oi the insu lating bushing ill@ to secure it to the oilset horlzontal portion il@ of the lJ-shaped bracket A spring ibo is coiled about .the pivot pin dit to bias the U-shaped bracket lli in a ccuinter-N clockwise direction about its pivot axis 95.

The operation of the compensating bimetallic strip lub in. Fig. 3 is as follows. When the am bient temperature rises, the bimetallic trip ele rnc-nt i2@ will be affected and will iler; slightly in the same direction itv would flex ii an overload current passed through it, namely, to the right toward the operating mechanism of the breaker. However, at the same time the bimetallic strip @dit will also be affected by the rising ambient temperature and will consequently flex in an upward direction toward the base Since the spring itil biases the U-shaped bracket ui in a counter-clockwise direction about its pivot axis til, the movement of the free end of the bi cern the position of adjusting screw l2? relative to the horn-shaped projection |25; and the amount of latch overlap, or" more particularly, the length of the end |33 engaged by the iinshaped metallic insert |3| remains constant irrespective of changes in ambient temperature.

Conversely, when the ambient temperature decreases, the bimetallic trip element |29 will be affected 'and will bend toward the left away from the operating mechanism of the circuit breaker. However, at the same time the bimetallic strip |03 will also be affected by the decreasing ambient temperature, and will bend downward away from the base This movement of the free end of the bimetallic strip |93 downward will pull the U- shaped bracket 8| about its pivot pin 85 in a clockwise direction against the biasing action of the spring |65. Consequently, the bending to the left of the free end of the bimetallic trip element |29 is compensated by the clockwise rotation of the U-shaped bracket 8|, which supports the bimetallic trip element |29, and the position of the adjusting screw |21 relative to the hornlshaped projection |25 remains unchanged irrespective of the decreasing ambient temperature.

Instead of using a steel wire in the connection between the two bimetallic elements |29 and |03, a iiexible metallic ribbon or any other flexible connection could be used since the element is always under tension.

The use in Fig. 1 of the spring IIS to bias the bracket 8|, causes the adjusting screw |09 to be engaged at all times by' insulator III, and in Fig. 3 the spring |65 biases the insulating bushing |59 into engagement with the washer IBI on the steel wire |51 and in each case eliminates all lost motion or free play between the bimetallic trip element and the compensating bimetal. This causes the bimetals 19 and |29 to follow exactly everyv movement of the compensating bimetals |03. The resultv of such a novel connection between these two vital elements of the circuit breaker is uniform breaker tripping irrespective of changes in ambient temperature.

In Fig. 3 it will be noticed that the hole |2| in the base is made relatively small to insulate the compensating bimetallic strip |03 from heat in the interior of the circuit breaker casing, and also to minimize the circulation of oil through this opening whenv the circuit breaker is used in oil-immersed applications.

It will be noticed in both embodiments of the invention that as a consequence of bracket 83 being rigidly secured to the base by the clinched over ends of members 81 and the main supporting brackets 31 and |43 being riveted to the base by means of the rivets 39 and |01 there cannot possibly be a relative displacement between brackets 83 and 31 or |43 along the base to change the amount of latch travel in the breaker.

While the invention has been disclosed in accordance with the provisions of the patent statutes, it is to be understood that various changes in the structural details thereof may be made without departing from the spirit of the invention. It is desired, therefore, that the appended claims be given the broadest reasonable interpretation permissible in the light of the prior art.

I claim as my invention:

1. In a circuit interrupter, relatively movable contacts for opening and closing the circuit, a bodily movable thermal control element heated in response to the current in the circuit and movable in response to predetermined overload conditions in the lcircuit to effect actuation of said contacts, and a thermally responsive member having one portion rigidly secured to a xed support and having a free portion connected to said control element to bodily displace the same in compensating for changes in ambient temperature, said connection comprising a laterally flexible member which transmits the motion of the free portion of the thermally responsive member to said control element to bodily displace the same.

2. In a circuit interrupter, relatively movable contacts for opening and closing the circuit, a thermal control element movable in response to predetermined overload conditions in the circuit to effect actuation of said contacts, a laterally flexible rod-shaped member secured at one end to said control Velement and insulated therefrom, and a thermally responsive member having one portion rigidly secured to a fixed support and having a free portion connected to said control element to bodily displace the same in compensating for changes 'in ambient temperature` said connection comprising an adjusting screw in response to the current in the circuit and bendable in response to predetermined overload conditions in the circuit to effect actuation of said contacts, a member secured to said thermal control element, a thermally responsive member having one portion rigidly secured to a fixed support and having a freeportion connected to said control element to bodily displace the same about its pivot to compensate for changes in ambient temperature, and a biasing spring acting at all times to take up any lost motion in said connection, said connection comprising a thrust member which engages the member secured to the bodily movable control element to transmit the motion of the free end of said thermally responsive member to said control element, the point of engagement of said engaging members being disposed substantially on a center line between the pivot axis of the control element and the fixed portion of said thermally responsive member.

4. In a circuit interrupter, relatively movable contacts for opening and closing the circuit, a pivotally mounted thermal control element heated in response to the current in the circuit and bendable in response to predetermined overload conditions in the circuit to effect actuation of said contacts, an insulation thrust receiving member rigidly secured to said thermal control element, a thermally responsive member having one portion rigidly secured to a fixed support and having a free portion connected to said control element to move the same about its ,pivot to compensate for changes in ambient temperature, and a biasing spring acting at all times to take up any lost motion in said connection, said connection comprising an adjustable thrust member adjustably secured to the free end of the thermally responsive member and at all times engaging under compression said insulation member, the point of engagement of said thrust members being located substantially on a center line between the pivot axis of the control element and the fixed portion of said thermally responsive member.

5. In a circuit interrupter, relatively movable contacts for opening and closing the circuit, a

pivotally mounted bimetallic trip element heated in response to the current in the circuit and movable in response to predetermined overload conditions to cause opening of said contacts, and a bimetallic member having one end rigidly secured to a fixed support and having the other end connected to saidpivotally mounted bimetallic trip element by a laterally flexible member to rotate said pivotally mounted bi-metallic trip element in compensating the same for changes in ambient temperature.

6. In a circuit interrupter, relatively movable contacts for opening and closing the circuit, a pivotally mounted bimetallic trip element heated in response to the current in the circuit and movable a predetermined amount in response to predetermined overload conditions to cause opening of said contacts, a member secured to said pivotally mounted bimetallic trip element, a bimetallic member having one end rigidly secured to a xed support and having the other end connected to said pivotally mounted bimetallic trip element to rotate the same in compensating for changes in ambient temperature, and a biasing spring acting at-all times to take vup any lost motion in said connection, said connection comprising a thrust member which engages the member secured to the pivotally mounted bimetallic trip element to transmit the motion of the free end of the bimetallic member to rotate said pivotally mountedV bimetallic trip element, the point of'engagement oi said engaging members being disposed substantially on a center line between the pivot axis or the trip element and the fixed end of said binietallic member. f

"1. In a circuit interruptor, relatively movable contacts for opening and closing the circuit, a :pivotally mounted birnetallictrlp element heated in response to the current in the circuit and movable in response to predetermined overload conditions in the circuit to cause opening of said cona laterally 'exible member secured at one end to said trip element and insulated therefrom, and a bimetallic member having one end rigicly secured to a fixed support and having theother end connected to said pvotally mountedbimetaille trip element to rotate the same in compenfor changes in ambient temperature, said connection comprising an adjusting screw threaded through the free end'oi said bimetallic member, said screw being secured to one end of said laterally ilexible member. f l

S. ln a circuit interrupter, relatively movable contacts ior opening and closing the circuit, a oivotally mounted bimetallic trip element heated response to the current in the circuit and movable in response to predetermined overload cc-nditions in the circuit to cause opening of said contacts, an insulation thrust receiving member rigidly secured to said pivotally mounted bime' tallic trip element, a bimetallic member having one end rigidly secured to a fixed support and having the other end connected to said pivot allymounted bimetallic trip element to rotate the same in compensating for changes in ambient temperature, and a biasing spring acting at all times to take up any lost motion in said connection. said connection comprising an adjustable thrust member threaded through the free end of said bimetallic member which engages said insulation member, one of said engaging thrust me; bers having a rounded surface for engaging the other member, and the point of engagement of said rounded surface with said insulation member being disposed substantially on a center line bei tween the pivot axis of said trip element and the fixed end of said bimetallic member.

9. In a circuit interrupter, relatively movable contacts for opening and closing the circuit. a,

pivotally mounted thermal control element heatedin response to the current in the circuit and movable in response to predetermined overload conditions in the circuit to effect actuation of said contacts, and a bimetallic member having one end rigidly secured to a xed support and having the other end connected to said pivotally mounted control element to rotate the same in compensating for changes in ambient temperature, said connection comprising a thrust member responsive to movement of the free end of said bimetallic member, said thrust member engaging a rounded surface that is movable with said control element. the point of engagement being near a center line drawn between the pivot axis of' said pivotally mounted thermal control element and the fixed end of said bimetallic member.

10. In an electrical switch, a casing, a switch member mounted in' said casing for movement to open and to closed circuit position, a thermal control element mounted in said casing heated by the current in the circuit and movable when heated a predetermined .amount by the passage oi currents or predetermined magnitude and duration to cause movement of said switch member to onev or its circuit controlling positions, and a thermally responsive member mounted on the outside of said casing and connected to said vthem/iai control element for compensating the same ior changes in ambient temperature, said connection comprising a laterally ilexible membe' which transmits the motion of said thermally responsive member to said thermal control element.

il. ln an electrical switch, a casing, a switch member mounted in said casing for movement to open and to closed circuit position, a pivotallif mounted electro-responsive control element mounted in said casing, said element being movin response to predetermined current conditions to cause movement of said switch member to one olf its circuit controlling positions, a inember secured to said electro-responsive .control element, a thermally responsive member mountcasing, said i-,ifiernaally responsive member being connected to said control element to compensate said control element for changes in ambient temperature, said thermally responsive member having one portion rigidly secured to the casing of the electrical switch and having a -free portion from. whic said connection is made, and a biasinf., spring at all times to tale up any lost motion in said connection, said connection comprising a thrust member which engages said member secured to said control element to transmit the motion of the iree portion of said thermally responsive member to said control element, the point ci engagement of said engaging thrust members being disposed substantially on a center iine between the pivot axis oi said control element and the fixed portion of said thermally responsive member.

l2. In an electrical switch, a casing, a switch member mounted in said casing for movement to open and to closed circuit position, an electroresponsive control element mounted in said easing, said element being movable in response to predetermined current conditions tocause movement of said switch member to one of its circuit controlling positions, and a. thermally responsive member mounted outside of said casing so as to be responsive only to temperatures adjacent the outside ci the casing, said thermally responsive member being connected to said'control element to compensate said control element for changes in ambient temperature, said thermally responsive member having one portion rigidly secured to the casing of the electrical switch and having a free portion :from which said connection is made, said connection comprising a flexible cord member which transmits the motion of the free portion of said thermally responsive member to said control element.

13. in a circuit interrupter, a casing, relatively movable contacts mounted in said casing, a bimetallic trip element pivotally mounted in said casing and heated in response to the current flowing in the circuit, said trip element flexing a predetermined amount in response to predetermined overload conditions to cause opening of said contacts, an insulation member rigidly secured to said bimetallic trip element, a bimetallic member mounted outside of said casing jacent the outside of the casing and connected to said trip element to move said trip element about its pivot to compensate for changes in ambient temperature, said bimetallic member having one portion rigidly secured to the casing of the circuit interrupter and having a free portion from which said connection is made, and a biasing spring acting at all times to take up any lost motion in said connection, said connection `comprising an adjustable thrust member threaded through ,the free portion of said bimetallic member which engages the insulating member secured to said trip element to transmit the motion of the free portion of said blmetallic member to said trip element to bodily displace the same, the point of engagement of said engaging thrust members being disposed substantially on a center line between the pivot axis of said trip element and the fixed portion of the compensating member.

14. In a circuit interrupter, a casing, relatively movable contacts mounted in said casing, a bimetallic trip element bodily movable in said casing and heated in response to the current iiowing in the circuit, said trip element flexing a predetermined amount in response to predetermined overload conditions to cause opening of said contacts, a laterally flexible rod-shaped member secured at one end to said trip element and insulated therefrom, and a bimetallic member mounted outside of said casing so as to be responsive only to temperatures adjacent the outside oi7 the casing and connected to said trip element to bodily displace said trip element for changes in ambient temperature, said bimetallic member having one portion rigidly secured to the casing of the circuit interrupter and having a, free portion from which said connection is made, said connection comprising an adjusting screw threaded through the free portion of said bimetallic member, said screw being secured to one end of said laterally flexible rod-shaped member.

15. A circuit controlling means comprising a base, a bimetallic control element pivotally mounted on said base and heated in response to the current flow in the controlled circuit, said bimetallic element flexing inv response to predetermined overload conditions and also flexing in response to changes in ambient temperature, a member secured` to said bimetallic control element, a thermally responsive member rigidly secured at one end to said base on the opposite side thereof from said control element and havso as to be responsive only to temperatures ading its free end connected to said control element to move the same in compensating tor ambient temperature movement of said control element, and a biasing spring acting at all times to take up any lost motion in said connection. said connection comprising a thrust member which engages the member secured to said control element to transmit the motion of the free end of said thermally responsive member to said control element to bodily move the same, and the point of engagement of said engaging thrust members being disposed substantially on a center line between the pivot axis of said control element and the ilxed end of said thermally responsive member.

16. A circuit controlling means comprising a base, a -bimetallic control element bodily movably mounted on saidl base and heated in response to the current flow in the controlled circuit, said bimetallic element flexing in response to predetermined overload conditions and also flexing in response to changes in ambient temperature, and a thermally responsive member rigidly secured at one end to said base on the opposite side thereof from said control element and having its free end connected to said control element to bodily move the same in compensating for ambient temperature movement ol.' said control element, said connection comprising a. exible cord which transmits the motion of the free end of said thermally responsive member to said bimetallic control element to bodily move the same. 17. In a circuit breaker having relatively mov- I able contacts, a pivotally mounted bimetal control element heated in response to the current of the circuit and operable in response to predetermined overload conditions to cause actuation of said contacts, an ambient temperature compensating bimetal element flxedly mounted at one end, means operatively connecting the free end portion of said compensating bimetal element to said control element said connecting means including a connection which permits movement of said elements relative to each other without binding as the compensating bimetal element moves the control element about its pivot in compensating for changes in ambient temperature, at least a part of the said connection being disposed on a center line between the pivot axis of the control element and the fixed end of the compensating element, and spring means for taking u-p play in said connection.

HABLAN s. GANO. 

